Research by the mental health charity Mind shows an incredible four out of five 18-34 year-olds admit to putting on a brave face when they feel anxious. Children might also display feelings of anxiety in a different way to adults, so if you're a parent you need to know the signs. Here are just some of the things to look out for with friends, family and co-workers:

1. They say they feel physically ill

Anxiety often leads to physical symptoms such as headaches and stomach pains. With panic attacks, people may feel physical symptoms such as chest pains and shortness of breath, but not be aware they're having a panic attack. Anxiety can also make certain physical illnesses such as eczema much worse. Rachel Boyd, Information Manager at mental health charity Mind, adds:

"For some people, the focus of anxiety might be physical health meaning they spend lots of time worrying that they may have a serious illness or feeling very conscious of any physical health problems."

Especially if they're children…

It can be difficult for children to handle anxiety as they don't always have the necessary language to articulate how they feel. Anxious children may start 'acting out.' An anxious child may start wetting the bed, having frequent toilet accidents in the day, lashing out at other children and refusing to eat certain foods. Other anxious children may be excessively clingy or have frequent tantrums.

"Often anxious children may complain of frequent physical illnesses such as having stomach aches or headaches. It can be easier for a child to talk about physical symptoms that psychological symptoms."

2. Their sleep is disturbed

People suffering with anxiety can often feel tired because their bodies over produce adrenaline, which switches them into flight or fight mode. However, it is also true that many experiencing anxiety find it affects their ability to sleep, as anxiety can often feel worse at night when there is less by way of a distraction, according to Anxiety UK. Dr Silver says:

"Often people who are anxious may either sleep excessively or, alternatively, many people with anxiety have problems falling asleep or wake up several times in a night. Some anxious people have nightmares or night terrors."

3. They need excessive reassurance

Anxiety has an effect on both the body and mind. Psychological symptoms include feeling nervous and tense, thinking about a worrying situation over and over again and feeling like other people are noticing your anxiety.

"You may also notice that someone asks you for lots of reassurance, or seems much less confident about things they'd normally be ok with."

4. Their eating habits have changed

Feeling anxious can have a knock-on effect to eating habits, so sufferers may eat more or less than they previously did. As a result of stress, children may change their eating behaviours too by restricting their food, bingeing or purging. Dr Silver says:

"Often people who are very anxious will be unable to eat as they may have no appetite. Other people may restrict their eating or binge as a way of numbing the feelings of anxiety."

5. They've developed perfectionist tendencies

While one common sign is a lack of interest in physical appearance, a less obvious manifestation of anxiety could be the exact opposite. Some people with anxiety may also be anxious about their appearance and spend a lot of time and money trying to look 'perfect.' At work, anxiety may mean someone becomes overly perfectionistic, taking a long time to complete work.

This can be hard to notice in a lot of situations because, as well as being perfectionists – to some degree – those with anxiety disorders are often said to be people who are natural people pleasers, over-thinkers, compassionate, intelligent and responsible. So what you're looking for is an increase in these behaviours. Another manifestation of anxiety is obsessive behaviour. Dr Silver says:

"Obsessive behaviours such as excessive washing and checking might be a less obvious sign of anxiety in a loved-one."

6. They're finding it harder to focus

When a person is anxious, they're prone to ruminating over negative situations, which can contribute to difficulty concentrating. So you might notice an anxious person is frequently late for work or unable to focus on tasks they would normally do with ease.

7. Kids may want to skip school

When it comes to undiagnosed anxiety in children (much like an adult not being able to focus at work) sometimes anxiety means children have a harder time at school. The importance of school in a young person's life cannot be underestimated, yet anxiety has a tendency to affect this area of a child's life significantly, say Anxiety UK. Dr Silver says:

"Some children may avoid talking about school work, put off studying and avoid going to school."

8. They may not answer their phone

If a loved one starts avoiding activities they used to enjoy, or is spending more time alone, it could be a sign something's not alright. According to Anxiety UK, specific – but less obvious – signs of avoidance behaviour are getting taxis instead of using public transport, making excuses to avoid going out with family or friends, sitting at the end of the row in theatres or cinemas, always being accompanied when out and about, only shopping when it's quiet, using minor roads to avoid busier ones and crossing the street to avoid people. Rachel says:

"Anxiety sufferers may find they feel like running away or escaping, or spending lots of time and energy working out how to avoid anxious situations. If you experience social anxiety you might also avoid situations that could trigger your anxiety, such as meeting up with friends, going out shopping or even answering the phone."

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